Method for preparing hydrocarbylhydrocarbyloxysilanes

ABSTRACT

A method for preparing a hydrocarbylhydrocarbyloxysilane of formula R a H p Si(OR)(4 -a-b ), where each R is independently a hydrocarbyl group and subscript a is 1 to 4 and subscript b is 1 to 2 is disclosed. The method includes heating ingredients including a hydrocarbyl carbonate and a source of silicon and catalyst. The method can be used to make dimethyldimethoxysilane.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage filing under 35 U.S.C. § 371 of PCT Application No. PCT/US2019/047377 filed on 21 Aug. 2019, currently pending, which claims the benefit of U.S. Provisional Patent Application No. 62/728,091 filed 7 Sep. 2018 under 35 U.S.C. § 119 (e). PCT Application No. PCT/US2019/047377 and U.S. Provisional Patent Application No. 62/728,091 are hereby incorporated by reference.

TECHNICAL FIELD

Hydrocarbylhydrocarbyloxysilanes, such as alkylalkoxysilanes, can be prepared by direct synthesis using a hydrocarbyl carbonate and a catalyzed source of silicon. The method may avoid the need to use halosilanes and halogenated hydrocarbons in the production of hydrocarbylhydrocarbyloxysilanes.

BACKGROUND

Hydrocarbylhydrocarbyloxysilanes, such as alkylalkoxysilanes (e.g., dimethyldimethoxysilane, methyltrimethoxysilane, and trimethylmethoxysilane) are intermediates in the silicones industry useful for the production of various silicone fluids and resins. Alkylalkoxysilanes can be produced commercially by alkoxylation of alkylhalosilanes. When an alkylhalosilane reacts with an alcohol, the resulting alkoxylation reaction produces an alkylalkoxysilane product and a hydrogen halide by-product.

Typically, hydrocarbylhalosilanes are produced commercially by the Mueller-Rochow Direct Process, which comprises passing a halogenated hydrocarbon, such as methyl chloride, over zero-valent silicon in the presence of a catalyst and various promoters to produce a mixture of hydrocarbylhalosilanes. A typical commercial process to make zero-valent silicon comprises the carbothermic reduction of SiO₂ in an electric arc furnace at extremely high temperatures.

In addition to the Direct Process, alkylhalosilanes have been produced by the alkylation of silicon tetrachloride and various alkylchlorosilanes by passing the vapors of these chlorosilanes together with an alkyl halide over finely divided aluminum or zinc at elevated temperatures. However, this process results in the production of a large amount of by-product aluminum chloride or zinc chloride, which is costly to dispose of on a commercial scale.

There is an industry need to produce hydrocarbylhydrocarbyloxysilanes in processes that minimize the use of halogenated hydrocarbons and/or minimize production of undesirable by-products.

SUMMARY

A method for preparing a hydrocarbylhydrocarbyloxysilane comprises: heating at a temperature of 150° C. to 400° C., ingredients comprising

-   -   a) a hydrocarbyl carbonate, and     -   b) a catalyzed source of silicon, and     -   optionally c) hydrogen, and         thereby forming a reaction product comprising the         hydrocarbylhydrocarbyloxysilane, where the         hydrocarbylhydrocarbyloxysilane has formula         R_(a)H_(b)Si(OR)_((4-a-b)), where each R is independently a         hydrocarbyl group and subscript a is 1 to 4 and subscript b is 0         to 2.

DETAILED DESCRIPTION

The hydrocarbyl carbonate used as ingredient a) in the method described herein is commercially available. The hydrocarbyl carbonate may have formula:

where each R¹ and each R² are independently a hydrocarbyl group. R¹ and R² may each be independently selected from the group consisting of alkyl, alkenyl, alkynyl, and aryl. Alternatively, R¹ and R² may each independently be an alkyl group, an alkenyl group or an aryl group. Alternatively, R¹ and R² may each be an alkyl group. Alternatively, one of R¹ and R² may be an alkyl group and the other of R¹ and R² may be an aryl group. The alkyl groups for R¹ and R² may each have 1 to 10 carbon atoms, alternatively 1 to 6 carbon atoms, and alternatively 1 to 4 carbon atoms. The alkenyl and/or alkynyl groups for R¹ and R² may each have 2 to 10 carbon atoms, alternatively 2 to 6 carbon atoms, and alternatively 2 to 4 carbon atoms. The aryl groups for R¹ and R² may each have 6 to 10 carbon atoms, alternatively 6 to 8 carbon atoms. Alkyl, alkenyl, and alkynyl groups containing at least three carbon atoms may have a branched or unbranched structure. Alternatively, R¹ and R² may each be Me, Et, Pr, hexyl, or Ph. Alternatively, R¹ and R² may each be Me or Et. Alternatively, R¹ and R² may each be Me. Examples of hydrocarbyl carbonates useful in the method described herein include dimethyl carbonate, diethyl carbonate, methyl phenyl carbonate, diphenyl carbonate, dibenzyl carbonate, and diallyl carbonate, and they are commercially available from Sigma-Aldrich. The amount of hydrocarbyl carbonate may be 70 mol % per hour based on the amount of silicon in ingredient b), alternatively 50 mol % to 100 mol % per hour based on the amount silicon in ingredient b).

Ingredient b) is a catalyzed source of silicon. The silicon in ingredient b) is reactive with ingredient a). Ingredient b) may be a copper silicide or a contact mass such as that used in the Mueller-Rochow Direct Process, described above, which comprises silicon metal and a catalyst such as copper.

In one embodiment, ingredient b) is a copper silicide. The copper silicide used as ingredient b) in the method described above may have an empirical formula Cu_(z)Si_(y)Al_(x)Sn_(w)Ti_(v) where subscripts z, y, x, w, and v represent the molar amounts of each element present, and z>0, y>0, x≥0, w≥0, and v≥0, with the proviso that z>y. Alternatively, 2.5≤z≤8, and y=1. When x=w=v=0, then the copper silicide is a binary copper silicide. Alternatively, 3<z≤7 and y=1.

The copper silicide useful in the method may be a binary copper silicide, which is commercially available. “Binary copper silicide” means a material including both silicon and copper that are intermixed at an atomic level, and the arrangement of the atoms can be described using well known crystallographic principles and models. Example phases of binary copper silicides are found in the phase diagram (Okamoto H., J. Phase. Equilib., Vol. 23, 2002, p 281-282) and include, but are not limited to: Cu_(0.88)Si_(0.12), Cu_(0.85)Si_(0.15), Cu_(0.83)Si_(0.17), Cu_(4.15)Si_(0.85), Cu₁₅Si₄, and Cu_(3.17)Si. In addition, binary copper silicide may further include Cu and Si individually, provided that the amount of Cu present is not sufficient to cause sintering in the method described herein. Exemplary binary copper silicides include, but are not limited to, Cu₇Si, Cu₅Si, Cu₄Si, and Cu₃Si. Other exemplary binary copper silicides include, but are not limited to, κ-Cu₇Si, γ-Cu₅Si, δ-Cu_(4.88)Si, ε-Cu₄Si, and η-Cu₃Si. Other exemplary binary copper silicides include, but are not limited to η-Cu₃Si, η′-Cu₃Si, η″-Cu₃Si, η-Cu_(3.17)Si, η′-Cu_(3.17)Si, and η″-Cu_(3.17)Si. Alternatively, the binary copper silicide may be Cu₅Si.

In one embodiment, the ingredients consist of ingredient a) and binary copper silicide, i.e., without hydrogen, used as ingredient b). In this embodiment, the binary copper silicide is typically at least 99.0% pure, alternatively 99.5% pure, or greater. The binary copper silicide may be 99.0% pure to 99.99% pure, alternatively 99.5% pure to 99.9% pure.

Alternatively, when ingredient b) is a copper silicide, the copper silicide may further comprise an additional metal, i.e., a different metal included in addition to copper and silicon. In this instance, additional metal may act as a co-catalyst even though it is incorporated into the copper silicide, and the copper silicide may be ternary or higher. The additional metal may be selected from aluminium (Al), tin (Sn), titanium (Ti), or a combination of two or more of Al, Sn, and Ti. This copper silicide may have an empirical formula Cu_(b)Si_(c)Al_(d)Sn_(e)Ti_(f) where subscripts b, c, d, e, and f, represent the molar amounts of each element present, and b>0, c>0, d≥0, e≥0, and f≥0; with the provisos that at least one of d, e, and f is not 0. In this copper silicide, b>c. Alternatively, 2.5≤b≤8, c=1, and one of d, e, and f is greater than 0. Alternatively, the additional metal may be selected from the group consisting of Al and Sn. Alternatively, the additional metal may be Al. Alternatively, the additional metal may be Sn. Alternatively, the copper silicide may have formula (M)_(i)(Cu_(k)Si)_(j), where M is the additional metal selected from Al, Sn, and Ti. Alternatively, M may be Sn or Ti. Alternatively, M is Sn. Subscript i represents the molar amount of the additional metal, and 0<i≤1. Subscript k represents the molar amount of copper relative to silicon, and 2.5≤k=8. Alternatively, 3≤k≤5. Subscript j represents the molar amount of copper and silicon collectively, relative to the amount of the additional metal, and j has a value sufficient that a quantity (i+j)=100. Exemplary copper silicides in this embodiment include ternary intermetallic compounds of Cu, Si, and Al; of Cu, Si, and Sn; and of Cu, Si, and Ti. Alternatively, the copper silicide in this embodiment may have formula (M_(m):Cu_((1-m)))_(n)Si, where M is as described above, subscript 0<m≤0.01; alternatively 0.001≤m≤0.01 and 2.5≤n≤8. Alternatively, M is selected from the group consisting of Al, Sn, and Ti. Alternatively, M is selected from the group consisting of Ti and Sn. Alternatively, M is Sn. Alternatively, M is Ti. Exemplary copper silicides of this formula include (Sn_(0.01)Cu_(0.99))₅Si, (Ti_(0.01)Cu_(0.99))₅Si, (Sn_(0.01)Cu_(0.99))₄Si, and (Ti_(0.01)Cu_(0.99))₄Si, (Al_(0.01)Cu_(0.99))₃Si. These copper silicides are commercially available. Alternatively, they may be prepared by conventional methods, such as from the melt of the individual elements at predetermined stoichiometry using a heating apparatus such as electric arc melter. Alternatively, the ternary intermetallic compounds may be prepared by a process comprising vacuum impregnating two metal halides on silicon particles thereby producing a mixture, and mechanochemically processing the mixture under an inert atmosphere, thereby producing a reaction product comprising the ternary copper silicides. The copper silicides described above may be prepared in this manner.

Alternatively, the method may further comprise adding ingredient d) a promoter or co-catalyst. Ingredient d) may be used, for example, in the embodiment in which a binary copper silicide is used as ingredient b). In this embodiment, ingredient d) is a separate metal or compound added with the copper silicide, i.e., not a metal incorporated in the ternary or higher copper silicide. Ingredient d) may be selected from Al, Sn, Ti, or a combination of two or more of Al, Sn, and Ti. The catalyst may be metallic, e.g., metallic Sn or metallic Al. Alternatively, the catalyst may comprise one or more compounds of Al, Sn, or Ti. Compounds are exemplified by halides, e.g., chlorides such as aluminium chloride (AlCl₃), stannous chloride (SnCl₂), and stannic chloride (SnCl₄), and/or zinc chloride (ZnCl₂); oxides such stannous oxide (SnO₂), and phosphides. The amount of ingredient d) can vary depending on the type and amount of species selected from the catalyst and desired distribution of the hydrocarbylhydrocarbyloxysilane species produced. However, the amount of catalyst may range from 1000 ppm to 3%, alternatively 0.5% to 3%, alternatively 1% to 3%, and alternatively 1% to 2%, based on the weight of ingredient b).

In an alternative embodiment, ingredient b) is a contact mass such as that used in the Mueller-Rochow Direct Process. The contact mass comprises silicon metal, a catalyst, and optionally a promoter. The catalyst may be copper, silver or nickel, alternatively copper. Any form of copper, silver, or nickel may be used. For example, when the catalyst is copper, the catalyst may be selected from elemental copper, copper alloys, copper compounds, and mixtures thereof. Examples of the copper compounds include, but are not limited to, granular copper powder, stamped copper, cuprous oxide, cupric oxide, cupric chloride, cuprous chloride, copper nitride, copper hydroxide, copper formate, and mixtures of two or more of the preceding copper compounds. Methods of making such copper compounds are known in the art, and the compounds are available commercially. The contact mass may include an amount of copper or copper compound sufficient to provide 2 ppm to 10%, alternatively 0.2% to 10% of elemental copper based on the weight of elemental silicon in the contact mass.

The promoter can be any element or its compounds that accelerate or catalyze the Direct Process. Promoters include, but are not limited to, phosphorous, phosphorous compounds, zinc, zinc compounds, tin, tin compounds, antimony, antimony compounds, arsenic, arsenic compounds, cesium, cesium compounds, aluminium and aluminium compounds, calcium, calcium compounds, titanium, titanium compounds, and mixtures of at least two of the preceding promoters. Alternatively, the promoter may comprise one or more elements selected from zinc, tin, iron, phosphorous and aluminium. One or more promoters may be present in the contact mass in amounts such that elemental phosphorus may be present in amounts of up to 2500 ppm, alternatively 250 to 2500 ppm based on the weight of the silicon in the contact mass. Elemental tin may be present in an amount of up to 200 ppm, alternatively 5 ppm to 200 ppm, based on the weight of silicon in the contact mass. Elemental aluminium and elemental iron may each be present in amounts up to 1%, alternatively 0.02% to 1%, based on the weight of silicon in the contact mass. Elemental zinc may be present in an amount up to 10,000 ppm, alternatively 100 to 10,000 ppm based on the weight of silicon in the contact mass. Exemplary phosphorus promoters include elemental phosphorus, metal phosphides such as zinc phosphide. Certain compounds may include more than one promoter, such as tin phosphide. Alternatively, catalyst and promoter may be provided in one compound, such as when a copper-zinc alloy such as brass, a copper-antimony alloy, or a copper-phosphorous alloy, such as cuprous phosphide, is combined with silicon metal to form the contact mass.

When promoter is present, the combination of catalyst and promoter may be present in the contact mass in a combined amount of 3 ppm to 10% based on the weight of silicon metal in the contact mass, alternatively 3 ppm to 5%. One skilled in the art would recognize that metallurgical grade silicon used in preparation of the contact mass may contain one or more impurities that act as a catalyst and/or a promoter as described above. Examples of contact masses and how to make them are described in patents, for example, U.S. Pat. Nos. 8,962,877; 5,596,119; 5,059,343; 4,966,986; 4,965,388; 4,962,220; 4,946,978; 4,898,960; 4,762,940; 4,602,101; and U.S. Re. 33,452. In one embodiment, ingredient b) is a contact mass comprising silicon, copper, and tin.

The method can be performed in any reactor suitable for the combining of gases and solids or any reactor suitable for the combining of liquids and solids. For example, the reactor configuration can be a batch vessel, packed bed, stirred bed, vibrating bed, moving bed, re-circulating beds, or a fluidized bed. Alternatively, the reactor for may be a packed bed, a stirred bed, or a fluidized bed. To facilitate reaction, the reactor may have means to control the temperature of the reaction zone, i.e., the portion of the reactor in which the ingredients are in contact.

The temperature of the reactor in which the ingredients are contacted is at least 150° C., alternatively 150° C. to 400° C.; alternatively 200° C. to 350° C.; alternatively 200° C. to 300° C.; alternatively 250° C. to 350° C.; alternatively 350° C. to 400° C.; alternatively 370° C. to 400° C.; and alternatively 300° C. to 400° C. Without wishing to be bound by theory, it is thought that if temperature is less than 150° C., then the reaction may not proceed at a sufficient speed to produce the desired product; and if the temperature is greater than 400° C., then ingredient a) and/or hydrocarbylhydrocarbyloxysilanes in the reaction product may decompose.

The pressure at which the ingredients are contacted can be sub-atmospheric, atmospheric, or super-atmospheric. For example, the pressure may range from greater than 0 kilopascals absolute (kPa) to 2000 kPa; alternatively 100 kPa to 1000 kPa; and alternatively 101 kPa to 800 kPa.

The mole ratio of ingredient a) to ingredient b) may range from 10,000:1 to 0.01:1, alternatively 100:1 to 1:1, alternatively 20:1 to 5:1, alternatively 20:1 to 4:1, alternatively 20:1 to 2:1, alternatively 20:1 to 1:1, and alternatively 4:1 to 1:1. The amounts of ingredient a) and ingredient b) are sufficient to provide the mole ratio described above.

The residence time for ingredient a) is sufficient for the ingredient a) to contact ingredient b) and form the reaction product. For example, a sufficient residence time may be at least 0.01 s, alternatively at least 0.1 s, alternatively 0.1 s to 10 min, alternatively 0.1 s to 1 min, and alternatively 0.5 s to 10 s. The desired residence time may be achieved by adjusting the flow rate of ingredient a), or by adjusting the total reactor volume, or by any combination thereof.

Ingredient b) is used in a sufficient amount. A sufficient amount of ingredient b) is enough to form the reaction product, when ingredient a) is contacted with ingredient b). The exact amount of ingredient b) depends upon various factors including the type of reactor used (e.g., batch or continuous), the residence time, temperature, the molar ratio of ingredient a) to ingredient b), and the particular species selected for ingredient a) used. However, a sufficient amount of ingredient b) may be at least 0.01 milligram per cubic centimeter (mg/cm³) of reactor volume; alternatively at least 0.5 mg/cm³ of reactor volume, and alternatively 1 mg/cm³ of reactor volume to the maximum bulk density of the ingredient b), alternatively 1 mg/cm³ to 5,000 mg/cm³ of reactor volume, alternatively 1 mg/cm³ to 1,000 mg/cm³ of reactor volume, and alternatively 1 mg/cm³ to 900 mg/cm³ of reactor volume.

There is no upper limit on the time for which the method is conducted. Without wishing to be bound by theory, it is thought that the method may be performed indefinitely to make the reaction product as ingredient a) is contacted with ingredient b). For example, the method may be conducted for at least 0.1 s, alternatively 1 s to 30 hours (h), alternatively 1 s to 5 h, alternatively 1 min to 30 h, alternatively 3 h to 30 h, alternatively 3 h to 8 h, and alternatively 3 h to 5 h.

The method described herein may also comprise purging before contacting the ingredients. Purging may be conducted to remove unwanted gaseous or liquid materials. Unwanted materials are, for example, air, O₂ and/or H₂O. Purging may be accomplished with a gas such as argon (Ar), helium (He), hydrogen (H₂), and/or nitrogen (N₂); alternatively H₂; alternatively an inert gas such as Ar, He, and/or N₂. Purging may be performed by feeding the gas into the reactor at ambient or elevated temperature, such as 25° C. to 300° C.

The method may further comprise vaporizing ingredient a), such as by known methods, e.g., heating or passing a carrier gas through a reservoir containing ingredient a), before contacting with ingredient b).

The method may further comprise recovering the reaction product, for example, to purify one or more of the hydrocarbylhydrocarbyloxysilanes in the reaction product produced by the method. The reaction product may be recovered by, for example, removing gaseous reaction product and any other vapors from the reaction product followed by condensation of the vapors and/or isolation of one or more compounds from any other compounds in the reaction product by a technique such as solvent extraction and/or distillation.

The hydrocarbylhydrocarbyloxysilanes produced by the present method may have formula R_(a)H_(b)Si(OR)_((4-a-b)), where each R is independently a hydrocarbyl group and subscript a is 1 to 4 and subscript b is 0 to 2. Each R be independently selected from the group consisting of alkyl, alkenyl, alkynyl, and aryl. Alternatively, each R may independently selected from an alkyl group, an alkenyl group or an aryl group. Alternatively, each R may be an alkyl group. The alkyl groups for R may each have 1 to 10 carbon atoms, alternatively 1 to 6 carbon atoms, and alternatively 1 to 4 carbon atoms. Alkyl groups are exemplified by Me, Et, Pr, and Bu. The alkenyl and/or alkynyl groups for R may each have 2 to 10 carbon atoms, alternatively 2 to 6 carbon atoms, and alternatively 2 to 4 carbon atoms. The aryl groups for R may each have 6 to 10 carbon atoms, alternatively 6 to 8 carbon atoms. Alkyl, alkenyl, and alkynyl groups containing at least three carbon atoms may have a branched or unbranched structure. Alternatively, each R may be independently selected from Me, Et, Pr, hexyl, or Ph. Alternatively, each R may be Me or Et. Alternatively, each R may be Me. Alternatively, subscript a may be 1 to 2 and subscript b may be 0 to 1. Alternatively, the hydrocarbylhydrocarbyloxysilanes produced by the method may have formula R_((4-a))Si(OR)_(a), where R and a are as described above.

Examples of hydrocarbylhydrocarbyloxysilanes produced by the present method include dimethylmethoxysilane (Me₂HSiOMe), trimethylmethoxysilane (Me₃SiOMe), methyldimethoxysilane (MeHSi(OMe)₂), dimethyldimethoxysilane (Me₂Si(OMe)₂), methyltrimethoxysilane (MeSi(OMe)₃), tetramethoxysilane (TMOS), and combinations of two or more of Me₂HSiOMe, Me₃SiOMe, MeHSi(OMe)₂, Me₂Si(OMe)₂, Me₂Si(OMe)₃, and TMOS. Alternatively, the product may comprise methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, and tetramethoxysilane.

The hydrocarbylhydrocarbyloxysilanes (such as alkylalkoxysilanes) may be used as reactants to make polyorganosiloxane resins with crosslinked siloxane networks. Such polyorganosiloxane resins are useful, for example, for making high temperature coatings, as thermal and electrical insulating coatings, as hydrophobic coatings, and/or as matrices for fiber reinforced composites. Dialkyldialkoxysilanes, such as dimethyldimethoxysilane, are useful as reactants for producing polydialkylsiloxane polymers, such as polydimethylsiloxanes.

EXAMPLES

These examples are intended to illustrate some embodiments of the invention and should not be interpreted as limiting the scope of the invention set forth in the claims. Copper silicide of formula Cu₅Si with 99.5% purity and methyl phenyl carbonate were purchased from Alfa Aesar. Cu₅Si with 97% purity was purchased from Gelest. Dimethyl carbonate was purchased from ACROS.

Reference Example 1—Copper Silicide Preparation

Copper silicide ingots were prepared by high temperature melting of the precursor materials using a MRF model SA200 laboratory arc-melter. The general formula was M₅Si with M being either pure Cu or a mixture of copper with an additional metal other than copper in a ratio of copper to the other metal of 99:1, atomic ratio. The appropriate weight quantities of the precursor materials were mixed together and placed into an oxygen-free copper crucible. The process of forming the silicide was performed under Argon (Ar) atmosphere (80-90 kPa) using a standard ceriated tungsten electrode in three one minute sessions. Between the sessions the sample ingot was cooled to below 200° C., removed, surface cleaned and placed upside down back into the crucible. The subsequent repeated re-melting of the crucible contents assured a good homogeneity of the final copper silicide ingot, which was first confirmed by a visual inspection of the ingot and then by the XRD characterization. The interaction between the melt and the crucible was minimal, as no wetting of the crucible surface by the melt was observed during the synthesis.

The copper silicide ingots were crushed with a vise to small chunks. The crushed ingots were then ground in air for 10 minutes using a Spex SamplePrep™ model 8000D mill. A 316 stainless steel ball mill vial and four 7 mm diameter tungsten carbide balls were used in the grinding process, which resulted in formation of a copper silicide powder with the average particle size of <150 μm, as determined by sieving (80 mesh sieve). A tungsten carbide ball mill vial and two 10 mm tungsten carbide bearings were also used in the grinding process.

The reactor apparatus included a gas flow preparation system, an 18″ long (0.25″ outer diameter and 0.15″ diameter) quartz reactor tube, a tube furnace, an in-line gas sampling valve, and a GC equipped with mass-selective and thermal conductivity detectors. The gas flow preparation system allowed for an individual supply or pre-mixing of any of two gases or gas streams: H₂ and Ar. The gas flows were controlled in the 2-100 sccm range for Ar and H₂ using Brooks 5850 thermal mass flow controllers. The mass flow controllers were equipped with metal seal valves and pre-calibrated for the specific gases by the manufacturer. The hydrocarbyl carbonate was injected into the reactor tube via a ⅛″ tube which was fed by a pump. The pressure of the gas flow entering the reactor was monitored by a 1-2000 psi pressure range capacitance pressure transducer (0.1 psi accuracy) powered via an electronic readout unit. All gas lines between the mass flow controllers and reactor inlet were made of stainless steel tubing; all gas valves were of a ball-type lubricant-free from Swagelok®; all gas connectors, joints and other flow components were of a Swagelok® tube type. The Parker® fluoro-polymer compression fittings were used to connect the quartz reactor tube to the gas preparation system and the sampling valve. The front portion of the reactor before the furnace and the area between the ends of the furnace were heated at 110° C. by heating tape controlled by two AC current variable transformers. A Lindberg/Blue M HTF55122A type furnace with the 0-1200° C. temperature range was used for the reactor temperature control. The furnace PID controller allowed for better than 0.5° C. temperature stability at 350° C., which was the reaction temperature used in these examples. The reactor tube outlet was connected to the in-line heated six-way sampling valve (Valco Vici®). The 1/16″ O.D. stainless steel tube gas sampling loop attached to the valve was of 100 μl volume. The temperature of the valve and the loop was maintained at 200° C. The gas lines between the reactor unit and sampling valve and between the sample valve and the bubbler were heated by an electric heating tape. The temperature of the heated tape maintained at 130° C. by an AC current variable transformer.

The quantitative analysis of the reactor effluent was performed chromatographically by using the thermal conductivity detector (TCD) of the on-line gas GC instrument. The identity of the compounds in the reactor effluent was determined using the mass-selective (MS) detector. The GC/MS instrument was an Agilent 5795 GC attached to a 5975C MS. The preferred GC conditions were to use 30 meter SPB-octyl LTM columns initially at 50° C. and then ramping to 150° C. (100° C./min) while holding for several minutes and cooling back to 25° C. Pressure was set at 15 psi and a flow rate of around 40 ml/min. A 25:1 split flow ratio was used, and data were collected for 10-13 minutes per sampling run (depending on substrate). A 200° C. inlet temperature was used to allow higher boilers to reach the column. Injections were performed automatically using the 6-way valve.

Example 1—Copper Silicide and Dimethyl Carbonate

In each trial, 3.09 g of a copper silicide that contained 0.25 g of silicon was placed in the ¼″ quartz tube and this was placed in the reactor. The copper silicide was treated at 300° C. under a flow of 20 sccm hydrogen for 30 minutes to remove any surface oxides that may have been present. Then, the reactor was heated at 350° C. under a flow of 5 sccm Ar. Next, the desired flow rate of 10 microliters/min (which corresponds to 2.6 sccm of gaseous dimethyl carbonate) was started. The reaction progress was monitored by sampling and analyzing the reactor gas effluent as described above. Table 1 (see last page of this application) shows the copper silicide sample used and the amounts (mol %) of each species present in the reaction product. These examples showed that use of a binary copper silicide and use of a ternary copper silicide having certain additional metals present in addition to copper and silicon can be used to produce a reaction product with high selectivity to dimethyldimethoxysilane.

Example 2—Contact Mass

In an additional trial, a sample of silicon (HSC 890 from Hemlock Semiconductor Corporation of Hemlock, Mich., U.S.A.) was combined with copper catalyst (CuCl) and tin promoter (SnCl₂) to form a contact mass. Three samples were also prepared containing HSC890 and 1000 ppm titanium, 1000 ppm aluminum, and 1000 ppm titanium and aluminum each. These three samples were then combined with copper catalyst and tin promoter as described above, and the resulting contact masses were evaluated using the equipment and procedure described above. The results can be seen in Table 2.

Example 3—Copper Silicide and Diethyl Carbonate

An amount of 3.09 g of Alfa Aesar Cu₅Si was placed in a ¼″ quartz tube and this was placed in the reactor. The Cu₅Si was heated to 300° C. under a flow of 20 sccm hydrogen for 30 minutes to remove any surface oxides that may have been present. Then, the carrier gas was switched to 5 sccm Ar. Next, 0.2 ml of diethyl carbonate was injected into the reactor. After priming, the flow rate was set to 0.0051 ml/min of diethyl carbonate (1 sccm diethyl carbonate). The reaction progress was monitored by sampling the gas effluent periodically. The TCD integral values of the reaction intermediates were input into a spreadsheet to determine values such as selectivity, rate, conversion, and silicon removed. After 60 minutes the tube effluent contained 58 mol % EtSi(OEt)₃, 41 mol % Si(OEt)₄, and >1% disiloxanes and other ethyl silanes. The conversion of diethyl carbonate to ethylethoxysilanes was 34.8 mol %. The integral silanes production rate was 19.3 μmol/min.

Example 4—Copper Silicide and Diphenyl Carbonate

In an argon filled glove box 0.865 g (2.5 mmol) Cu₅Si (high purity) was placed in a 38 mL Ace Glass pressure tube (1″×10″ with a #15 thread and inner viton o-ring) and 1.06 g (5 mmol) of diphenyl carbonate was also charged. The tube was removed from the glove box and placed in a heating block and heated to 300° C. The portion of the tube protruding from the heating block was wrapped in aluminum foil. After running for 20 hours, the reactor was cooled and then the contents were taken up in CDCl₃. The resulting solution was analyzed by GCMS, which showed Si(OPh)₄, PhSi(OPh)₃, and Ph₂Si(OPh)₂ with the ratio of starting material to Si(OPh)₄ being 1:0.045, the ratio of Ph₂Si(OPh)₂:Si(OPh)₄ being 0.041:1, and the ratio of PhSi(OPh)₃:Si(OPh)₄ being 0.22:1.

Example 5—Binary Copper Silicide with SnCl₂ Promoter

The procedure of example 1 was repeated, except 3.09 g of a physical mixture of 8 mg of SnCl₂ (8 mg) and the balance Cu₅Si was placed in the reactor instead of the copper silicide of example 1. The results are in Table 1. Example 5 shows that a separate metal compound added with the copper silicide, i.e., not a metal incorporated in the ternary or higher copper silicide can also provide the benefit of the method described herein.

INDUSTRIAL APPLICABILITY

The method described herein is capable of preparing hydrocarbylhydrocarbyloxysilanes without need of preparation of a hydrocarbylhalosilane first and then converting the hydrocarbylhalosilane via, e.g., an alkoxylation reaction. The method conditions are similar to those of Rochow-Muller direct process, except with different starting materials. Without wishing to be bound by theory, it is thought that the method described herein is a more environmentally friendly approach (as compared to the Rochow-Muller direct process) that reduces or avoids the need to use halogenated hydrocarbons (such as methyl chloride) which are considered less environmentally friendly agents (due to the subsequent HCl generation upon preparation of siloxane polymers). Therefore, the present method may be performed without adding any halide of formula R′X (where R′ is hydrogen or a hydrocarbyl group and X is a halogen atom as described above) during step 1), as recited in claim 1. Furthermore, the present method may be performed without adding halosilanes during step 1), which can also result in HCl generation upon preparation of siloxane polymers.

Without wishing to be bound by theory, it is thought that adding ingredient c) hydrogen while feeding the dimethyl carbonate may result in a decrease in reaction rate (as compared to the same conditions where hydrogen is not used), and may increase the relative amounts of Me₃SiOMe and MeSi(OMe)₃ species in the reaction product. Without wishing to be bound by theory, it is thought that when diethyl carbonate used in place of dimethyl carbonate under the conditions of the examples above, will provide selectivity towards ethyl triethoxysilane in the reaction product; and methyl phenyl carbonate used in place of the dimethyl carbonate will improve selectivity toward the formation of Si-Me and Si—OPh bonds (instead of Si-Ph and Si—OMe bonds).

The Brief Summary of the Invention and the Abstract are hereby incorporated by reference. All ratios, percentages, and other amounts are by weight, unless otherwise indicated. The articles ‘a’, ‘an’, and ‘the’ each refer to one or more, unless otherwise indicated by the context of the specification. Abbreviations used herein are defined in Table A, below.

TABLE A Abbreviations Abbrev. Word % Percent AC alternating current Bu “Bu” means butyl and includes branched and linear structures such as iso-butyl and, n-butyl. ° C. degrees Celsius Et Ethyl GC gas chromatograph and/or gas chromatography ICP-AES inductively coupled plasma atomic emission spectroscopy ICP-MS inductively coupled plasma mass spectrometry kPa Kilopascals Me Methyl mg Milligram mL Milliliters mol mole Ph Phenyl Pr “Pr” means propyl and includes branched and linear structures such as iso-propyl and, n-propyl. s Seconds sccm standard cubic centimeters per minute TCD thermal conductivity detector μmol micromole Vi Vinyl

“Metallic” means that the metal has an oxidation number of zero.

“Purging” means to introduce a gas stream into a container to remove unwanted materials.

“Treating” means to introduce a gas stream into a container to pre-treat a component before contacting the component with another component. Treating includes contacting ingredient b) with the gas stream to reduce or otherwise activate ingredient b) before contacting it with ingredient a).

“Residence time” means the time which a component takes to pass through a reactor system in a continuous process, or the time a component spends in the reactor in a batch process. For example, residence time in step 1) refers to the time during which one reactor volume of ingredient b) makes contact ingredient a) as ingredient b) passes through the reactor system in a continuous process or during which ingredient b) is placed within the reactor in a batch process. Alternatively, residence time may refer to the time for one reactor volume of reactive gas to pass through a reactor charged with ingredient b). (E.g., residence time includes the time for one reactor volume of ingredient a) to pass through a reactor charged with ingredient b).

The disclosure of ranges includes the range itself and also anything subsumed therein, as well as endpoints. For example, disclosure of a range of 2.0 to 4.0 includes not only the range of 2.0 to 4.0, but also 2.1, 2.3, 3.4, 3.5, and 4.0 individually, as well as any other number subsumed in the range. Furthermore, disclosure of a range of, for example, 2.0 to 4.0 includes the subsets of, for example, 2.1 to 3.5, 2.3 to 3.4, 2.6 to 3.7, and 3.8 to 4.0, as well as any other subset subsumed in the range.

With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination with any other member or members of the group, and each member provides adequate support for specific embodiments within the scope of the appended claims. For example, disclosure of the Markush group: alkyl, alkenyl and aryl includes the member alkyl individually; the subgroup alkyl and aryl; and any other individual member and subgroup subsumed therein.

It is also to be understood that any ranges and subranges relied upon in describing various embodiments of the present disclosure independently and collectively fall within the scope of the appended claims, and are understood to describe and contemplate all ranges including whole and/or fractional values therein, even if such values are not expressly written herein. The enumerated ranges and subranges sufficiently describe and enable various embodiments of the present disclosure, and such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and so on. As just one example, a range “of 150 to 400” may be further delineated into a lower third, i.e., from 150 to 233, a middle third, i.e., from 234 to 316, and an upper third, i.e., from 317 to 400, which individually and collectively are within the scope of the appended claims, and may be relied upon individually and/or collectively and provide adequate support for specific embodiments within the scope of the appended claims. In addition, with respect to the language which defines or modifies a range, such as “at least,” “greater than,” “less than,” “no more than,” and the like, it is to be understood that such language includes subranges and/or an upper or lower limit. As another example, a range of “at least 0.1%” inherently includes a subrange from 0.1% to 35%, a subrange from 10% to 25%, a subrange from 23% to 30%, and so on, and each subrange may be relied upon individually and/or collectively and provides adequate support for specific embodiments within the scope of the appended claims. Finally, an individual number within a disclosed range may be relied upon and provides adequate support for specific embodiments within the scope of the appended claims. For example, a range of “1 to 9” includes various individual integers, such as 3, as well as individual numbers including a decimal point (or fraction), such as 4.1, which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.

The subject matter of all combinations of independent and dependent claims, both singly and multiply dependent, is expressly contemplated but is not described in detail for the sake of brevity. The disclosure has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described.

TABLE 1 Int. DMC Si Conv. Prod. Silicon Source Me₂HSiOMe Me₃SiOMe MeHSi(OMe)₂ Me₂Si(OMe)₂ MeSi(OMe)₃ TMOS “SiOSi” to Si Rate Cu₅Si′* 0 14 0 73 10 0 3 7.6 13.7 Cu₅Si^(‡)* 0 31 0 51 12 1 5 13.8 29.0 Cu₅Si^(†)* 0 5 0 15 39 40 1 1.3 2.3 (Cu_(0.99)Ti_(0.01))₅Si^(†) 2 14 0 36 28 20 0 0.9 1.6 (Cu_(0.99)Ni_(0.01))₅Si^(†) 0 6 0 16 39 39 0 0.3 0.6 (Cu_(0.99)Al_(0.01))₅Si^(†) 0 0 0 0 0 0 0 0 0 Cu₅Si/SnCl₂ ^(†)° 7 13 0 70 9 0 1 2.1 3.5 In Table 1, * = same conditions were repeated three times, ^(‡) = copper silicide purchased Gelest; ′ = copper silicide purchased from Alfa Aesar; ^(†) = copper silicide made according to Reference Example 1 with high purity Si, Cu, and M; and ° = physical mixture of Cu₅Si with 1000 ppm SnCl₂. TMOS refers to tetramethoxysilane of formula Si(OMe)₄. Dimethyl carbonate was supplied at 2.6 sccm (0.01 ml/min) and there was a 5 sccm Ar carrier gas. All reactions were carried out at 350° C., 1 atmosphere pressure for 70 minutes. All values reported in (mol %) except the rate data with is represented in (μmol/min). Without wishing to be bound by theory, it is thought that the amount of Al was too high when incorporated in the copper silicide under the conditions of example 1, and this resulted in the poor reactivity because too much Al may have decomposed the hydrocarbyl carbonate. It is thought that a lower amount of Al in the silicide would provide beneficial results, based on the results of Table 2, below.

TABLE 2 Direct reaction of contact masses made with doped silicon, SnCl₂, and CuCl with DMC after 70 minutes at T = 350° C., P = 1 atm. All values in (mol %) except for the rate, which is in (μmol/min). DMC Conv. Int. Si Sample Me₂HSiOMe Me₃SiOMe MeHSi(OMe)₂ Me₂Si(OMe)₂ MeSi(OMe)₃ TMOS “SiOSi” to Si Prod. Rate 1 14 10 5 61 10 0 0 1.3 1.4 2 13 16 2 56 13 0 0 1.5 1.6 3 9 17 1 58 15 0 0 1.3 1.4 4 4 14 6 62 13 1 0 0.8 0.8

In Table 2, in each example dimethyl carbonate was supplied at 2.6 sccm, Ar carrier was supplied at 5 sccm, 1 g Si metal was used, 176 mg CuCl was used, and 8 mg SnCl₂ was used. Sample 1 also contained 950 ppm Ti. Sample 2 also contained 1310 ppm Al. Sample 3 also contained 1100 ppm Ti and 1360 ppm Al. Sample 4 was prepared without additional Ti or Al. 

The invention claimed is:
 1. A method comprises: 1) heating at a temperature of 150° C. to 400° C., ingredients comprising a) a hydrocarbyl carbonate, and b) a copper silicide; thereby forming a reaction product comprising an hydrocarbylhydrocarbyloxysilane of formula R_(a)H_(b)Si(OR)_((4-a-b)), where each R is independently a hydrocarbyl group and subscript a is 1 to 4 and subscript b is 0 to
 2. 2. The method of claim 1, where the hydrocarbyl carbonate is selected from dimethyl carbonate, diethyl carbonate, diphenyl carbonate, or methyl phenyl carbonate.
 3. The method of claim 1, where the copper silicide has empirical formula Cu_(z)Si_(y)Al_(x)Sn_(w)Ti_(v) where subscripts z, y, x, w, and v represent the molar amounts of each element present, and z>0, y>0, x≥0, w≥0, and v≥0, with the proviso that z>y.
 4. The method of claim 1, where the copper silicide is a binary copper silicide.
 5. The method of claim 1, where the copper silicide is Cu₅Si.
 6. The method of claim 1, where the copper silicide comprises copper, silicon and an additional metal selected from the group consisting of aluminium, tin, titanium, and combinations of two or more of aluminium, tin, and titanium.
 7. The method of claim 1, further comprising adding d) a promoter.
 8. The method of claim 7, where the promoter comprises aluminium, tin, titanium, or a combination of two or more of aluminium, tin, and titanium.
 9. The method of claim 1, further comprising adding c) hydrogen during step 1).
 10. The method of claim 1, where each R is methyl, ethyl or phenyl.
 11. The method of claim 1, where the hydrocarbylhydrocarbyloxysilane comprises methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, and tetramethoxysilane.
 12. The method of claim 1, where the reaction product comprises a hydrocarbylhydrocarbyloxysilane of formula R₂Si(OR)₂.
 13. The method of claim 1, further comprising purging and/or treating ingredient b) before step 1) and/or 2) recovering the hydrocarbylhydrocarbyloxysilane from the reaction product. 